When the motor is energized, it functions as a transformer, with the secondary being short-circuited, requiring a starting current that is much larger than the nominal current, which can reach about eight times its value. The high starting currents cause inconveniences, therefore, demand dimensioning of cables with diameters much thicker than necessary. In addition, best industrial wastewater evaporation momentary power factor drops may occur, causing power bills to rise.
The very time consuming starts occurring when the motor torque is only slightly higher than the robust torque: the over-current absorbed, dangerously heats the motor while the rated speed is not reached. Likewise, a countercurrent stop, that is, by inverting the motor, will represent the cost equivalent to three starts. In all cases, it is critical to ensure that the starting conjugate is sufficient.
To avoid these high starting currents, there are methods of motor drives, which guarantee a reduction in the starting current value of these machines, such as: star-delta start; Match series-parallel; Start by spherical; Started by Soft Starter; Start by Frequency Inverter.